Since H. pylori was found as a bacterium living in the stomach by Warren et al. in 1983 (Lancet, I. 1273 (1983)), attentions have been paid to the relationship between H. pylori and chronic gastritis, gastric ulcer and duodenal ulcer. Recently, it has been found that gastric gland cancer is caused in mongolian gerbil infected with H. pylori without administering any carcinogens (Watanabe et al., Gastroenterology, 115, 642 (1988)), and thus the relation of H. pylori with gastric cancer as a causal bacterium has also been suggested. In addition, it has been increasingly clarified that the recurrence of peptic ulcer in H. pylori-positive patients with peptic ulcer can be prevented by disinfecting H. pylori. Various methods for disinfecting H. pylori from the stomach have been studied.
In order to disinfect gastric H. pylori without using antibiotics, a method using Lactobacillus gasseri OLL 2716 (L. gasseri OLL 2716) having a high disinfection potency against H. pylori (which has been deposited on Jan. 14, 2000 as Accession No. FERM BP-6999 in National Institute of Bioscience and Technology, Agency of Industrial Science and Technology (Higashi 1-1-3, Tsukuba, Ibaraki, Japan) [present name: International Patent Organism Depositary, National Institute of Advanced Industrial Science and Technology (AIST Tsukuba Central 6, 1-1, Higashi 1-Chome Tsukuba-shi, Ibaraki-ken, Japan)] (also called “LG21”) has been proposed (JP-A-2001-143 and EP 1 112 692 A1). The Lactobacillus gasseri strain OLL 2716 was found as the result of screening studies on a large number of lactobacillus bacteria derived from human intestines, a bacterial strain having the following characteristics: (1) high resistance to gastric acid; (2) good growth under low pH conditions; (3) high potency to suppress the adherence of H. pylori onto human gastric cancer cell MKN45; (4) high potency to suppress the growth of H. pylori during co-culture with H. pylori in mixture; (5) high potency to disinfect H. pylori when dosed in H. pylori-infected model mouse; and (6) high survival, good flavor and physical properties when applied to food products. Particularly, since the strain is excellent in production properties (preservability, flavor and physical properties) in preparing fermented milk, it is preferable to administer the strain in the form of fermented milk. Thus, disinfection of H. pylori using the antibacterial effect of lactobacillus can be considered as a convenient and effective method without any side effects. However, fermented milk has a relatively short quality preservation period of about 2 weeks due to food properties of fermented milk. After 2 weeks preservation, the bacterial count decreases to almost half the level before preservation. Namely, fermented milk is not suitable for long preservation.